Organic co-antiknock agents



United States Patent Delaware N0 Drawing. Filed Mar. 22, 1961, Ser. No. 97,451 12 Claims. (Cl. 44-69) This invention relates to an improved gasoline composition for spark ignition internal combustion engines, more particularly to a gasoline composition with improved knock resistance.

Knock in spark ignition engines is generally considered to be caused by an abnormally rapid combustion of an unburned fuel-air mixture in front of the normal flame front. A severe pressure unbalance due to this rapid combustion process sets up shock waves which impinge upon the cylinder walls and pistons to produce the characteristic metallic knocking noise.

The need for high quality fuels, having increased resistance to knock over a wide range of engine operating conditions is of paramount significance in current engine operation. Careful refining and blending of fuel components can produce a fuel of sufficiently increased knock resistance to satisfy engine requirements under certain stressed conditions. The resistance to detonation by such fuel is even further augmented by the addition of organometallic antiknock agents such as lower alkyl lead compositions, tetraethyllead (TEL), for example, and various other organometallic compositions such as methylcyclopentadienyl manganese tricarbonyl. TEL is widely used today for the improved antiknock quality which it imparts over a broad range of engine operating conditions. The use of TEL, however, has limitations, especially that each successive increment of TEL added to the fuel produces only a fraction of the improvement in antiknock rating obtained with the addition of the preceding increment. Moreover, certain fuels for spark ignition engines, particularly those containing high amounts of aromatic and/or olefinic components, respond rather poorly to TEL, particularly at the normal upper limit of about 4.2 grams of lead/ gallon of fuel in automotive engines and about 7.4 grams of lead/ gallon of fuel in aviation engines.

Resistance to knock is evaluated in terms of octane numbers. When the octane number of a motor gasoline fuel is raised, there is generally a concomitant decrease in the susceptibility of such fuel to further octane number improvement by the addition of organ-o-metallic antiknock agents. Therefore, it becomes less economical to obtain further resistance to knock 'by employing organo-metallic antiknock agents in higher concentrations with high octane fuels.

It is an objective of this invention to provide improved high octane gasoline fuel compositions containing octane improving amounts of antiknock agents. It is also an object of this invention to extend the effectiveness of certain organo-metallic antiknock additives in high octane gasolines. It is a further object of the invention to increase the detonation resistance of gasolines containing such additives without increasing either the toxicity of the fuel composition or its tendency to lay down combustion chamber deposits. A still further object of the invention is to provide improved gasoline fuel compositions in which the effectivenes of certain antiknock additives is increased in an economical manner. Other objects will be apparent in the description of the invention.

It is well known in the art that certain organic materials such as tertiary 'butyl acetate can be employed as sup-plementary octane i-mprovers for leaded gasolines. These materials cooperate with the antiknock agent to increase its effectiveness and are referred to hereafter as co-antiknock agents. Generally, the co-antiknock agent should "Ice distribute along with the antiknock agent in a multicylinder engine and be effective over a wide range of co-antiknock to antiknock rnole ratios. In addition, a co-antiknock agent should preferably have the following physical properties: (1) be a water-white liquid, (2) boil in the motor fuel distillation range, (3) be miscible in gasoline at temperatures from the freezing point to the boiling point, (4) be practically insoluble in water, and (5) be no more toxic than the hydrocarbons and other additives in the mot-or fuel.

It has been found that when certain oxygenated materials are added in small amounts to high octane motor fuels (having Research Octane Ratings of about to about said fuels containing organometallic antiknock agents, such as lower alkyl lead compositions and other organo-metallic antiknock agents such as the class of manganese compounds disclosed in US. Patent to Brown et al. 2,818,417, issued December 31, 1957, that the octane number of the fuel composition is unexpectedly raised by as much as about 1.6 octane numbers, even though in the absence of organo-metallic antiknock agents, substantially no octane number benefit is obtained by the addition of these materials to the motor fuel. Moreover, both Research Method octane number (RON), and Motor Method octane number (MON) are increased. (By Research and Motor Methods for obtaining octane number, reference is made to ASTM test designations D90'8-55 and D35753, respectively.) These oxygenated co-antiknock agents exhibit optimum (Jo-antiknock grains over a Wide mole ratio range of co-antiknock agents to antiknock agent, i.e., mole ratios of 3 to are effective. As discussed infra in connection with Table III, optimum mole ratios of co-antiknock to antiknock exist below which co-antiknock benefits are negligible and above which smaller benefits or even proknock effects may occur.

The co-antiknock compounds of this invention are substituted lower alkyl monocar-boxylic esters which are composed solely of carbon, hydrogen and oxygen. These gas0line-soluble compounds can be more readily defined by the following structural formula:

In this formula R can be a primary or secondary alkyl or alkenyl radical containing up to 8 carbon atoms, an aryl or cycloalkyl radical containing up to 10 carbon atoms or an acetoalkenyl radical containing up to 8 carbon atoms. R and R can each be hydrogen atoms and alkyl or alkenyl radicals containing up to 8 carbon atoms.

X is a whole number from 0 to 1. The formula as defined above will be referred to hereafter as (I).

In a preferred embodiment of the invention, R is an alkenyl radical with the unsaturation at the a carbon atom, i.e., when X equals 1 R is preferably a vinyl r-adioal. When X equals 0 an acrylic ester is defined.

In a particularly preferred embodiment of the invention, R is a cycloalkyl radical, R and R are hydrogen atoms. For example, cyclohexyl acetate is a preferred co-antiknock agent, i.e.

It is readily apparent from the data set forth in Table II above that the co-antiknock materials of Formula I unexpectedly increase in co-antiknock activity in higher octane gasolines, whereas previously known co-antiknock agents such as tertiary butyl acetate show a decrease in co-antiknock effectiveness in high octane gasoline, i.e. tertiary butyl acetate had a ARON of 1.4 in a base fuel of 102 RON and a ARON of 1.0 in a base fuel of 110-113 RON.

The co-antiknock agents of Formula I are not effective in all gasoline motor fuels containing organo-metallic antiknock compounds. It has been found that in leaded gasoline an octane-improving amount of tetraalkyllead equal to about 0.1 gram of lead per gallon of fuel must be present in order to produce a significant cooperative effect. The lead concentration may be as high as about 18.6 grams of lead per gallon of fuel. It has been found that organo-manganese compounds should not be used with the co-antik-nock substances of the invention at higher concentrations that about 2.0 grams of manganese per gallon of fuel, but the co-antiknock compounds are highly effective in fuels containing any octane-improving amount of organo-manganese less than about 2.0 grams of manganese per gallon of fuel. Generally, a minumum octane number improving amount of organomanganese is an amount corresponding to about 0.05 gram of manganese per gallon of fuel. It is preferred that the fuel compositions of this invention contain at least 0.2 gram of lead per gallon of fuel or from 0.05 to 1.75 grams of manganese per gallon of fuel. The fuel can contain mixtures of the two antiknock materials so long as the concentrations of each is within the foregoing limits. Further the fuel can contain mixtures of the herein defined co-antiknock agents, for example, 0.2% v. cyclohexyl acetate and 0.4% v. ethyl rnethacrylate added to a fuel containing 3.186 grams lead as TEL produces a significant cooperative effect.

When improving the octane rating of fuels, the cost per unit octane number increase becomes greater at higher octane levels, requiring more extensive refining and conversion method's. Generally, the effectiveness of the antiknock agents decreases with each additional increase in antiknock concentration. be economical above about 3 to 4 grams of lead per gallon of fuel. It is at this point that the class of co-antiknocks as herein defined are most effective. For example, these co-antiknock agents are effective in producing significant increases in the octane rating of gasolines having RON of from about 105 to about 125, whereas conventional processing or doping costs to produce a corresponding octane increase is excessive. However, these co-antiknock additives are relatively ineffective in the 90 to 102 octane number range, where conventional processing, and the use of antiknock agents and certain other CO-Hl'lilkIlOCk materials are more economical.

The oxygenated additive-s of Formula I act as cooperative high level octane improvers, that is they display a coantiknock effect only when combined with certain o-rganometallic antiknock agents; in high octane gasolines, in fact, the co-antiknock effect is directly related to the type and concentration of the particular antiknock agent present. When added to a base hydrocarbon fuel which did not contain an antiknock agent, the class of compounds of Formula I were found to have no antiknock effect.

Water insolubility is an important physical property of co-antiknock agents. Generally, commercial gasolines contain a small amount of dissolved water (from .005 to 0.2% by volume). Such water is, of course, derived from the previous processing of the gasoline and gasoline precursors, for example, crude desolvent and steam stripping. Thus when commercial gasolines undergo cooling and storage or during transportation, the dissolved water tends to precipitate out of the fuel. It is therefore important that the co-antiknock additive contained in gasoline be resistant to such a leaching action by water. It is preferred to employ as co-antiknock agents materials For example, TEL ceases to which have low solubility in water as well as high solubility in the base fuel. Preferably the solubility of the co-antiknock agent in the base hydrocarbon fuel should be at least about 50% by weight while its solubility in water at normal storage temperatures should not exceed about 5% by weight. Vinyl acetate, for example, is nearly insoluble in water and highly soluble in the base fuel.

The co-antiknock materials of the invention are generally effective in pure hydrocarbons (i.e., less than 1% v. contaminants) in the gasoline boiling range, having a RON (with 3 cc. TEL/ gal.) from about to about 125, such as ethylbenzene and isooctane. Mixtures of pure hydrocarbons and/or of conventional gasoline refining process streams are likewise suitable, provided the RON (3 cc. TEL/ gal.) of the finished blend falls within the approximate 105 to range. Within the limits of the afore stated octane level restrictions, catalytic reformate, catalytically and thermally cracked gasolines, and motor alkylates are suitable to the invention. Especially preferred as blending components, however, are light aviation alkylates, iso-merizates, high severity reformates, reformate extracts, and pure aromatics suh as benzene, toluene and xylenes. It is further preferred that the finished gasoline contain appreciable amounts (i.e., 5 to 10% v. minimum) of each of two or more hydrocarbon types. Where there are only two hydrocarbons in a preferred embodiment of the invention, the hydrocarbon fuel is selected from the group consisting of mixtures of paraffins and olefins, mixtures of olefins and aromatics, mixtures of highly branched parafiins. In addition, certain oxygenated hydrocarbons such as lower alkyl alcohols and certain lower dialkyl ethers can be used in the gasoline in concentrations up to 20% by volume.

Within the foregoing limits of gasoline composition and antiknock concentration, the co-antiknock materials of the invention are effective in concentrations as low as 0.1% by volume. However, at least 0.2% by volume is preferred since substantial increases in both Motor Method and Research Method octane numbers are obtained by using at least this amount. The upper limit beyond which no substantial further increase in octane number is obtained by either the Research or Motor Method varies somewhat among the various effective co-antiknock agents as well as with the hydrocarbon composition and the particular antiknock material used. Preferred concentrations are from about 0.2 to about 1.5% by volume. Though greater amounts may be added, it has been found that little additional benefit is obtained by adding more than about 1.5% by volume. Moreover, certain compounds of Formula I exhibit proknock effects at concentrations above about 2.0% by volume.

It is to be understood that the order of mixing the various constituents of the compositions of the invention is immaterial. For example, the co-antiknock compound may be added to gasoline which already contains an organo-metallic antiknock compound. Likewise, the coantiknock and antiknock compounds may be first mixed, stored and handled as a concentrate and added to the gasoline at a later time. A gasoline additive concentrate of this latter type may also contain halogen scavenger compounds. In addition to the halogen containing lead scavengers, the fuel compositions of the invention can and ordinarily will contain other additives, for example, dyes, spark plug anti-foulants such as tricresyl phosphate, dimethyl xylyl phosphate, and diphenyl cresyl phosphate, combustion modifiers such as alkyl boronic acids and lower alkyl phosphates and phosphites, oxidation inhibitors such as N,N-ditertiarybutyl-4-methylphenol, metal deactivator such as N,N'-disalicylal-1,2 propanediamine, and rust inhibitors such as polymerized linoleic acids and N,C- di-substituted imidazolines, and the like. Under some circumstances it may be desirable to mix the halogen scavenger and the antiknock compound with the co-antiknock compound in the desired relative proportions and handle or store this mixture with or without stabilizers, anti-fouling compounds, inhibitors, etc., as a concentrate for incorporation with the other components of the ultimate fuel composition.

In addition to TEL, the co-antiknock agents of Formula I are also effective in fuels containing other organo-metallic compounds as antiknock agents. These include tetraalkyllead compounds such as tetramethyllead, tetra n-propyl lead, methyl triethyl lead, ethyl trimethyl lead, dimet-hyl diethyl lead and mixtures thereof and other organo-rnetallic materials such as cyclopentadienyl nickel nitrosyl, rnethcyclopentadienyl manganese tricarbonyl and related materials, tris-(acetylacetonate) iron-III, nickel Z-ethylhexyl salicylate, bis-(N-butyl salicylaldimine) nickel and vanadium acetylacetonate. However, the herein defined additives do not exhibit co-antiknock activity with all organo-metallic antiknock agents. For example, they exhibit proknock effect with iron pentacarbonyl and ferrocene. Moreover, the eifectiveness of these co-antiknock agents varies considerably with each organo-metallic material. Tetraalkyllead, cyclopentadienyl nickel nitrosyl, methylcyclopentadienyl manganese tricarbonyl and tris- (acetyl-acetonate) iron-III are therefore preferred organometallic antiknock agents for the fuel compositions of the invention.

It will generally be preferred that the additive concentrate contain an optimum or near optimum ratio of coantiknook compound to organo-metallic antiknock agent. This ratio is easily determined by observation of the octane number increase obtained while varying the amount of coantiknock added to separate samples of a given fuel containing a constant concentration of antiknock agent. The following table indicates optimum ratios for various organic co-antiknock additives.

8 Example V Motor gasoline containing:

20% v. pentenes 99.1% v. 80% v. isooctane Diethyl dimethyl lead 1.0 g. lead/gal. Alkyl methacrylate 0.4% v.

Example VI Motor gasoline containing:

70% v. olefins 30% v. aromatics, and having a) 99.7% v.

RON of 110 Methyl triethyl lead 0.1 g. lead/ gal.

Vinyl butyrate 0.2% v.

I Example VII Catalytic reformate having a RON of 105 99.1% v. Mixture of tetraethyllead and tetramethyllead 0.2 g. lead/ gal.

3,4-dimethyl-2-hexene propionate 0.5% v.

Example VIII TABLE III.OPTIMUM CO-ANTIKNOCK/TEL MOLE RATIOS Optimum Optimum Mole Octane Hydro- Co-antiknock additive Range, Ratio, Oo-anti- Benefit carbon percent v. knock/TEL AR-B Fuel Vinyl acetate 0. 3 6 11 O. 7 Isooctane. Cyclohexyl acetate 1. 1-1. 4 22 1. Do. Isopropyl acetate. 1. 4-1. 31 2. 0 Do. Ethyl phenyl acetate--- 1. 11. 3 19 0. 2 Do. Sec-Butyl methacrylate 0. 8-0. 9 1. 2 Do. Ethyl acetate- 1.4-1.6 38 1.9 Do.

The following examples of motor gasoline fuel compositions are suitable for use according to the invention.

Example I Isooctane 99.25% v. Tetraethyllead 2.7 g. lead/ gal. Vinyl acetate 0.75% v.

Example I] 2,2,4-trimethylpentane 99.6% v. Tetramet-hyllead 3.0 g. lead/gal. Isopropyl acetate 0.4% v.

Example III Motor gasoline containing:

70% v. ethylbenzenes v. hexanes 99.33% v. 10% v. isooctane Ethyl trime-thyllead 2.0 g. lead/gal. Ethyl acrylate 0.67% v.

Example IV Motor gasoline containing approximately:

80% v. olefins 20% v. naphthalenes, and having a 99.3% v.

RON of 105 Tetraethyllead 2.0 g. lead/ gal.

Sec-buty-l methacrylate 0.4% v.

Example IX Motor gasoline containing:

v. ethylbenzene 20% v, naphthenes Methylcyclopentadienyl manganese tricarbonyl 0.5 g. manganese/ gal.

n-Octyl methacrylate 0.8% v.

Example X Motor gasoline containing:

40% v. isooctane 15 v. tertiary butyl alcohol 99.3% v.

45 v. ethylbenzene Cyclopentadienyl nickel nitrosyl 0.5 g. nickel/ gal.

Example XIII Motor gasoline containing:

25% v. hexanes 75% v. ethylbenzenes Bis (N butyl salicylaldimine) nickel 0.5 g. nickel/ gal. Isopropylacetate 0.3% v.

Example XIV Isooctane 99.5% v. Vanadium acetylacetonate 1.0 g. vanadium/ gal. Ethyl acrylate 0.6% v.

Example XV Isooctane 99.5% v.

Mixture of:

Tetramethyllead, 0.3% W. Trimethyl ethyl lead, 4.3% w. Dimethyl diethyl lead, 20.1%

W. Methyl triethyl, 42.2% w. Tetraethyllead, 33.0% w.

3.186 g. lead/gal.

Vinyl acetate 0.5% v.

Example XVI Ethylbenzenes 99.5% v. Mixture of:

Tetramethyllead, 5.7% w.

Trirnethyl ethyl lead, 23.8%

Dimethyl diethyl lead, 37.5% 3.186 g. lead/ gal.

Methyl triethyl lead, 26.2% W.

Tetraethyllead, 6.8% w

Ethyl methacrylate 0.5% v.

Example XVII 50% v. isooctane 50% v. ethylbenzene Mixture of:

Tetramethyllead, 30.0% W. Trimethyl ethyl lead, 42.2%

W. Dimethyl diethyl lead, 22.2%

w. Methyl triethyl lead, 5.2% W. Tetraethyllead, 0.5% W Methyl acrylate 0.5% v.

Example XVIII A gasoline consisting of:

80% v. paraffins 20% v. olefins having a R-30N 99.2% v.

of about 107 3.186 g. lead/gal.

Example XXI A gasoline consisting of:

70% v. aromatics 30% v. olefins having a RON }99.2% v.

of about 109 Tetramethyllead 2 g. lead/ gal. Heptyl-a-allyl acetobutyrate 0.8% v.

Example XXII A motor gasoline having a RON of about 123 99.0% v. Tetraethyllead 4 g. lead/ gal. m-Xylyl a- 4-octenyl acetocaproate 1.0% v.

Example XXIII Isooctane 98.5% v. Tetraethyllead 2 g. lead/gal. Cyclohexyl-a-tolyl acetoacetate 1.5% v.

Example XXIV A motor gasoline having a RON of about 125 99.0% v. Tetraethyllead 2 g. lead/ gal. 2,3-diethylcyclohexyl-a-cumyl acetoacrylate 1.0% v.

I claim as my invention:

1. Gasoline for use in spark ignition internal cornbustion engines consisting essentially of a hydrocarbon base fuel, an octane number improving amount of a tetraalkyllead antiknock agent and an octane number improving amount but not more than 2.0% of the fuel of a gasoline soluble co-antiknock agent composed solely of carbon, hydrogen and oxygen having the structural formula:

wherein R is selected from the group consisting of alphaunsaturated alkenyl radicals containing up to 8 carbon atoms and cycloalkyl radicals having up to 10 carbon atoms and R and R are selected from the group consisting of hydrogen atoms, and alkyl and alkenyl radicals containing up to 8 carbon atoms.

2. The gasoline of claim 1 in which the co-antiknock agent is cyclohexyl acetate.

3. A gasoline motor fuel composition consisting essentially of hydrocarbon types selected from the group consisting of mixtures of paraffins and olefins, mixtures of olefins and aromatics, and mixtures of paraffins and aromatics; an octane number improving amount of a tetraalkyllead antiknock agent; and an octane number improving amount, but not more than 2.0% of the fuel, of a gasoline soluble co-antiknock agent composed solely of carbon, hydrogen and oxygen having the structural formula:

wherein R is selected from the group consisting of alphaunsaturated alkenyl radicals containing up to 8 carbon atoms and cycloalkyl radicals having up to 10 carbon atoms and R and R are selected from the group consisting of hydrogen atoms, and alkyl and alkenyl radicals containing up to 8 carbon atoms.

4. The gasoline motor fuel composition of claim 3 in which the hydrocarbon types are mixtures of paraffins and olefins.

5. The gasoline motor fuel composition of claim 3 in which the hydrocarbon types are mixtures of olefins and aromatics.

6. The gasoline motor fuel composition of claim 3 in which the hydrocarbon types are mixtures of parafifins and aromatics.

7. A hydrocarbon fuel of the gasoline boiling range for use in spark ignition internal combustion engines having a Research Octane Number from about to about and containing an octane number improving amount of a tetraalkyllead antiknock agent and at least 0.1% by volume but not more than 2.0% by volume of the fuel of a gasoline soluble co-antiknock agent composed solely of carbon, hydrogen and oxygen having the structural formula:

wherein R is selected from the group consisting of alphaunsaturated alkenyl radicals containing up to 8 carbon atoms and cycloalkyl radicals having up to carbon atoms and R and R are selected from the group consisting of hydrogen atoms, and alkyl and alkenyl radicals containing up to 8 carbon atoms.

8. A gasoline motor fuel composition having a Research Octane Number from about 105 to about 125 consisting essentially of hydrocarbon types selected from the group consisting of mixtures of parafiins and olefins, mixtures of olefins and aromatics, and mixtures of paraffins and aromatics; an octane number improving amount of a tetraalkyllead antiknock agent; and an octane number improving amount, but not more than 2.0% of the fuel, of a gasoline soluble co-antiknock agent composed solely of carbon, hydrogen and oxygen having the strucsisting of hydrogen atoms, and alkyl and alkenyl radicals containing up to 8 carbon atoms.

9. Gasoline for use in spark internal combustion engines consisting essentially of a hydrocarbon base fuel, an octane number improving amount of a tetraalkyllead antiknock agent, and an octane improving amount but not more than 2.0% of the fuel of ethyl phenyl acetate, ethyl-a-(Z-propenyl)-a-acetoacetate, or a mixture of ethyl methacrylate and secondary butyl acryl-ate.

10. The gasoline of claim 9 in which the co-ant-iknock agent is a mixture of ethyl methacrylate and secondary butyl acrylate.

11. The gasoline of claim 9 in which the co-antiknock agent is ethyl phenyl acetate.

12. The gasoline of claim 9 in which the co-antiknock agent 'is ethy1-a-(2-propenyl)-u-acetoacetate.

References Cited by the Examiner UNITED STATES PATENTS 2,228,662 1/ 1941 Holm 4470 2,334,006 11/1943 Holm 44-7O 2,818,416 12/1957 Brown et a1. 4468 2,818,417 12/1957 Brown et al. 4468 3,009,793 11/ 1961 Eckert et al. 44-70 FOREIGN PATENTS 107,863 6/ 1939 Australia. 571,921 10/1958 Belgium.

DANIEL E. WYMAN, Primary Examineri JULIUS GREENWALD, Examiner.

Y. M. HARRIS, Assistant Examiner. 

1. GASOLINE FOR USE IN SPARK IGNITION INTERNAL COMBUSTION ENGINES CONSISTING ESSENTIALLY OF A HYDROCARBON BASE FUEL, AN OCTANE NUMBER IMPROVING AMOUNT OF A TETRAALKYLLEAD ANTIKNOCK AGENT AND AN OCTANE NUMBER IMPROVING AMOUNT BUT NOT MORE THAN 2.0% OF THE FUEL OF A GASOLINE SOLUBLE CO-ANTIKNOCK AGENT COMPOSED SOLELY OF CARBON, HYDROGEN AND OXYGEN HAVING THE STRUCTURAL FORMULA: 